Hydrokinetic coupling apparatus, particulary for a motor vehicle

ABSTRACT

A hydrokinetic coupling device includes a piston (9) displaceable in an axial direction along a guide ring (6) mounted on a transversal wall (2). Stops (50) are provided on the wall (2) to limit the displacement of the piston (9).

The present invention relates to hydrokinetic coupling apparatus,especially for motor vehicles, such as is described in the documentWO-A-94/07058.

This apparatus comprises a wall which is orientated generallytransversely, and which is adapted to be coupled in rotation to adriving shaft and carries a guide ring fixed centrally on the said wall.This wall is part of a housing which surrounds a turbine wheel that isfixed in rotation to a driven shaft.

A piston is sealingly mounted for axial movement along the said ring,and defines, with the wall and the ring, a variable volume chamber whichis bounded on the outside by a disc and by friction liners, which areadapted to be gripped, respectively, between the piston and the disc,and between the disc and the wall.

Each friction liner is fixed to one of the elements consisting of thedisc and, respectively, the piston and the transverse wall between whichit is adapted to be gripped.

The transverse wall becomes inflated outwardly when the hydrokineticcoupling apparatus is driven in rotation by the driving shaft, due tothe presence of oil in the housing which constitutes a casing.

More precisely, the transverse wall swells to a greater extent in thecentre than in the region of the friction liners.

As a result, the guide ring, fixed to the transverse wall, follows themovement of the latter so that a relative movement occurs between thepiston and the guide ring, with the disadvantage that a poor surfacearea is then offered to the piston. This piston may even escape from theguide ring.

In general terms, the piston can, following the above mentionedinflation effect, cease to cover the sealing ring which is interposedbetween the latter and the guide ring, when the lock-up clutch isdisengaged.

It should be emphasised that ram-like impacts also occur, so thatrelative displacement is produced between the piston and the guide ring.

In addition, it is desirable to reduce axial size in the region of theguide ring.

An object of the present invention is to overcome these drawbacks in asimple and inexpensive way, and to respond to this requirement.

In accordance with the invention, abutment means, facing towards thetransverse wall and carried by the transverse wall, are provided forlimiting the movement of the piston in a direction away from thetransverse wall.

Thanks to the invention, the relative displacement effects between thepiston and the guide ring are reduced.

The piston follows the movement of the transverse wall, and the axialsize is reduced in the region of the guide ring.

The said guide ring offers a good surface area to the piston under allcircumstances, so that the piston is thus unable to escape from thelatter when the lock-up clutch is disengaged (or separated). Thisabutment thus limits the movement of the piston towards the turbinewheel.

Thus the piston runs no risk of interfering with the hub of the turbinewheel, or with a radial web of a torsion damper.

The abutment means in accordance with the invention enable the sealingring to be protected, by ensuring that it is covered under allcircumstances, for example by the piston. The variable volume chamber isthus always sealed.

In addition, the axial displacement of the piston between the positionsin which the lock-up clutch is disengaged (or separated), and in whichthe lock-up clutch is engaged (or bridged), is minimised, so that theresponse times are reduced.

The said abutment thus enables the tangential resilient tongues to bepreserved (by limiting the deflection of the latter), these tonguesbeing interposed in certain embodiments between the piston and thetransverse wall so as to couple the piston in rotation with the saidtransverse wall, while leaving the possibility for axial movement of thepiston to take place.

The abutment means may be mounted in the said chamber and be formed in adrive member, which is fixed to the transverse wall and which serves forfastening of the tangential tongues, which in this case are interposedbetween the piston and the said member.

This arrangement is favourable to the reduction in axial size betweenthe guide ring and the hub to which the turbine wheel is fixed.

The following description illustrates the invention with reference tothe attached drawings, in which:

FIG. 1 is a half view in axial cross section of part of a hydrokineticcoupling apparatus in accordance with the invention;

FIG. 2 is a view, shown partly cut away, in the direction of the arrow 2in FIG. 1, showing the tongues;

FIG. 3 is a view taken on the line 3--3 in FIG. 2;

FIG. 4 is a view similar to FIG. 3, for another embodiment.

As is known, and as is described in the document WO-A-94/07058, to whichreference can be made for more detail, a hydrokinetic coupling apparatusincludes, arranged in a common sealed housing, which is filled with oiland which constitutes a casing, a torque converter and a lock-up clutch1.

The casing, which in this example is of metal, constitutes a drivingelement, and is adapted to be coupled in rotation to a driving shaft,namely the crankshaft of the internal combustion engine in the case ofapplication to a motor vehicle.

The casing, which is of annular form, consists of two half shells,facing towards each other and sealingly secured together at their outerperiphery, typically by welding.

The first half shell 2, 3 is adapted to be coupled in rotation to thedriving shaft, and includes a generally transversely orientated annularwall 2 which is extended at its outer periphery by a generally axiallyorientated cylindrical wall 3.

The second half shell, which for simplicity, like the reaction wheel ofthe converter, is not shown, is so configured as to define an impulsewheel having blades which are fixed to the internal face of that halfshell. These blades face towards the blades of a turbine wheel 4, whichis secured by riveting or welding to a hub plate which is integral witha hub 5, the latter being splined internally for coupling it in rotationto a driven shaft, namely the input shaft of the gearbox in the case ofapplication to a motor vehicle. This shaft is recessed internally so asto define a channel, which enables oil to reach a guide ring 6 fittedaxially between the hub 5 and the transverse wall 2, and which issecured to the said wall 2.

This ring 6 is provided with a central centring nose 7 which projectsaxially, and the ring 6 is fixed centrally by a welded joint, the seamof which can be seen at 61 (FIG. 1) to the wall 2, which for thispurpose has a central axially orientated sleeve portion 60 turnedtowards the outside, and into which the centring nose 7 penetrates. Thering 6 also has an integral, transversely orientated, collar portion 8.The ring 6 is therefore shouldered, and is in contact, through itscollar portion 8 and after having been secured by welding, with theinternal face of the wall 2 that faces towards the hub 5.

A piston 9 is mounted for axial sliding movement along the annular outerperiphery of the collar portion 8, which is provided with a groove formounting an annular sealing ring 29. The piston 9 has an axiallyorientated central sleeve portion which is turned towards the wall 2 forits sliding movement along the collar portion 8. The piston 9, togetherwith the ring 6, the wall 2, and a disc 10, which carries frictionliners 11 secured on each of its faces, for example by adhesive bonding,defines a variable volume chamber 30 which is fed through the ring 6,the latter having for this purpose apertures, not indicated by referencenumerals, which are fed through the above mentioned channel in thedriven shaft. In this example, the apertures are formed in the collarportion 8, and comprise inclined portions which are open into a blindhole formed centrally in the ring 6. The disc 10 is fitted at the outerperiphery of the piston 9, and has lugs, radially outside the piston 9,at its outer periphery with an axially orientated portion, each of theselugs penetrating into a notch formed in a guide ring 12 at its innerperiphery. The disc 10 is thus coupled in rotation to the guide ring 12,with axial mobility, through a coupling of the tenon and mortice typeconsisting of lugs and notches.

The notches are formed in a transverse portion 14 of the guide ring 12.This transverse portion 14 is extended by an annular portion 15,orientated axially and serving to retain, radially on the outside, coilsprings 16 which are retained on the inward side by an annular retainingportion 17 of a plate element 18, which is extended radially inwardly bya radial web 19, the latter being secured by riveting to the radialplate portion of the hub 5 at the same time as the turbine wheel 4,which for this purpose has lugs, not shown, at its inner periphery.

In another version, this fastening may be obtained by welding. The webportion 19 has a set of holes (not shown) to allow oil to flow betweenthe piston 9 and the wheel 4.

In another version, the plate element 18 may be secured to the turbinewheel 4 directly by welding.

The plate element 18 has engagement portions 20 for engagement by thecircumferential ends of the springs 16. These portions 20 are formed inserpentine abutment bridges which extend from the inner periphery to theouter periphery of the retaining portion 17 of the plate element 18.This portion 17 is in the form of a half shell, and is offset axiallywith respect to the portions 14, 15 of the guide ring 12, which alsoconstitutes a half shell. The guide ring 12 has in the region of itsaxial portion 15 integral inward deformations 21 for abutment with theends of the springs 16. The portion 14 also has lugs 22 for abutment bythe ends of the springs 16. For more detail, reference should be made tothe document WO-A-94/1047058, and especially to FIGS. 24 to 28 of thelatter.

It will be noted that, except for the sealing ring 29 and liners 11, thecomponents of the hydrokinetic coupling apparatus are of metal, and aretypically sheet steel pressings.

Thus, the lock-up clutch 1 comprises a torsion damper 23 which islocated mainly between the turbine wheel 4 and the wall 2 at the outerperiphery of the first shell, with an input part 12 disposed radiallyoutwardly of the piston 9 and liners 11 and consisting of the guide ring12 in the form of a half shell 14, 15, coil springs 16, and an outputpart which consists of the plate element 18, the latter being again inthe form of a half shell, at its outer periphery.

The output part 18 is coupled in rotation to the turbine wheel 4, and inthis example to the hub 5 of the latter, while the input part 12 iscoupled in rotation to the disc 10, projecting radially with respect tothe piston 9. The input part 12 is thus coupled releasably via the disc10 and the liners 11 to the driving shaft, the said disc 10 with itsliners 11 being adapted to be gripped releasably between the piston 9and the wall 2, which constitutes a counter piston. The disc 10 iscoupled resiliently to the hub 5 and to the wheel 4.

The turbine wheel 4 is driven in rotation by the impulse wheel, byvirtue of the flow of fluid contained in the sealed housing or casing,and after the vehicle has been started, and in order to avoid anysliding effects between the turbine and impulse wheels, the lock-upclutch 1 provides direct solid coupling (or bridging) of the drivenshaft with the driving shaft, this being obtained by gripping of thefriction liners 11 and disc 10 between the piston 9 and the counterpiston 2, with the driven shaft being driven directly by the half shell2, 3.

In order to disengage (separate) the clutch 1, pressure is transmittedinto the chamber 30 via the channel in the driven shaft, the blind holein the ring 6 and the apertures in the latter. The said chamber 30 issealed by means of the ring 29 carried by the collar portion 8.

In the engaged or bridged position of the clutch 1 (in which the liners11 are gripped), the said chamber 30 is depressurised. This chamber 30is accordingly bounded on the outside by the disc 10 and the liners 11,the piston 9 and the wall 2 each having at its outer periphery a flat(transverse) friction surface for the liners 11.

It will be noted that the piston 9 is coupled in rotation to the wall 2of the first half shell 2, 3 by means of tangential resilient tongues40, which are spaced apart circumferentially at regular intervals, therebeing in this example four sets of tongues (FIG. 3). These tongues 40enable the piston to move axially. The tongues are attached to thetransverse wall 2 through an interposed annular member 44, which in thisexample is of metal and which is fixed sealingly to the wall 2, in thiscase by means of rivets 45, which in the present example are integralwith the latter, being formed for example by extrusion. At its innerperiphery, the annular member 44 includes, from place to place, lugs 48which are offset axially with respect to its main portion by which it isfastened to the wall 2. The tongues 40, which in this example consist oftwo tongues laid together, are fixed at their ends to the lugs 48 bymeans of rivets 43.

These tongues 40 extend generally tangentially with respect to acircumference of the assembly.

For the attachment of the other end of the tongues 40 to the piston 9,use is made of fastening means 41, 42, which, being adapted to extendgenerally through the tongues 40 and piston 9, comprise two parts,namely a first part 41 which is applied to the tongues 40 in advance, onthe side of the latter opposite to the piston 9, and a second part 42,which only need to be on the same side as the piston 9 in order toengage with the first part 41. The tongues 40 lie within the space thatextends radially between the friction liners 11 and the axis of theassembly, that is to say within the chamber 30 and axially between thewall 2 and the piston 9.

In the present case, the two-part fastening means 41, 42 is of the typehaving an upset bolt shank. The first part 41 comprises a shank with anengagement head in contact with the surface of the tongues 40 that facestowards the wall 2. The engagement head is disposed within the chamber30. The shank passes, with a clearance, through the associated aperturein the piston 9, and comprises a smooth first portion and a notchedfirst portion [sic]. This part 41 is fitted to the tongues 40 byforce-fitting its smooth portion, or in another version by rolling oradhesive bonding.

The second part 42 consists of a seaming ring which includes, on thesame side as the piston, a base portion of enlarged diameter, so as toprevent it from undergoing plastic flow into the through aperture in thepiston. The second part is arranged on the side of the surface of thepiston 9 opposite to the tongues 40, that is to say outside the chamber30.

As will have been understood, the ring 42 is squeezed so that the latterwill come into engagement with the notched portion of the shank 41. Inanother version, rivets of the POP type can be used.

In a further version, the first part may consist of a screw or a nut,which is secured, for example by adhesive bonding, to the lugs 40, thesecond part being in the form of a screw or a nut.

All of the arrangements described in the document FR 94 13205 filed onthe Nov. 4th 1994 may be envisaged.

As is known, when the hydrokinetic coupling apparatus is driven inrotation, it causes the two said half shells to be inflated due to thepresence of oil.

The transverse wall 2 of the first half shell inflates more towards thecentre, that is to say in the region of the guide ring 6, which alsoacts as a feed ring for the chamber 30, than in the region of the disc10.

The ring 6 therefore follows the movement of the wall 2, so thatrelative movement occurs between the piston 9 and the ring 6.

In order to overcome this drawback, the invention proposes to provideabutment means 50, facing towards the transverse wall 2 and carried bythe said wall 2, in order to limit the movement of the piston 9 in adirection away from the transverse wall 2.

The piston 9 therefore follows the movement of the central portion ofthe wall 2, and is coupled with the ring 6.

Thus, the sleeve portion of the piston overlies the ring 29 under allcircumstances, the latter therefore being protected. In addition, themovement of the piston 9 towards the web 19 and turbine wheel 4 islimited, so that it is possible to control the distance between thepiston 9 and the liner 11 when the clutch 1 is disengaged.

It is possible to reduce the distance between the piston 9 and the liner11 (FIG. 1) in such a way that the time of response for the gripping(bridging) of the clutch 1 is reduced.

In FIGS. 1 to 3, the said abutment means 50 are located in the chamber30, and are formed in the member 44 by which the tongues 40 arefastened, the abutment means 50 being fixed to the wall 2. Thetangential tongues 40 are in this example extended circumferentially at47 beyond the two-part fastening 41, 42 that secures the tongues 40 tothe piston 9.

The free end of each of the extensions 47 is adapted to cooperate withan abutment 46, which faces towards the wall 2 (FIGS. 2 and 3). Thisabutment 46 is part of the member 50 and extends locally parallel to thewall 2. It is press-formed in the lugs 48, which are offset axially withrespect to the main portion of the annular member 44.

A lug 48 therefore has an end portion for fastening of a rivet 43, andan abutment 46.

Thus, going from the main portion of the member 44, the cross section isdefined generally by cranked portions (or claws) with an axiallyorientated portion surrounding the free end of the tongues 40 (i.e. theextension 47), these being extended by a transversely orientated portion46, constituting the abutment means in accordance with the invention andadapted to cooperate locally with the surface of the tongues 40 thatfaces towards the piston 9, that is to say with the dorsal face of thetongues 40.

In a modified version (FIG. 4), the head of the portion 41 of thefastening 41, 42 may be extended circumferentially at 147 so as toengage with the abutment 46.

In this case, the extension 147 has an axial extension which is adaptedto cooperate with the abutment 46. It is therefore the dorsal face ofthe head of the part 41 which serves as a counter-abutment for theabutment 46.

In a further version, each head of the rivets 43 may be extended at 247so as to constitute the abutment means 50. In this case the dorsal faceof the tongues 40 is arranged to cooperate with the said extension 247,and more precisely with the surface of the latter which faces towardsthe piston 9.

It will be appreciated that in every case, the abutment means 50 enablethe tongues 40 to be protected by limiting their deflection, especiallywhen the lock-up clutch 1 is disengaged.

In addition, this solution has a short axial length because it actswithin the chamber 30.

The hub 5 may therefore come very close to the ring 6. It will beappreciated that the position of the abutment 46 with respect to thesaid extension 47, 147, 247 is determined in such a way as to avoid anyinterference between the piston 9 and the web 19 and the hub 5.

In a further version, the fastening means 41, 42 may consist of simplerivets or screws or bolts.

To this end, a sub-assembly, consisting of the drive member 44, thetangential tongues 40, and the piston 9, is made up in advance.

The piston 9 of the sub-assembly is centred with the aid of a centringpiece mounted in the sleeve portion 60, and the drive member is thenfastened by laser welding to the transverse wall 2. This welding iscarried out for example on the side of the surface of the transversewall 2 which faces away from the piston 9. This weld extends through thethickness of the wall 2, and partly through the thickness of the drivemember 44. The centring piece is then retracted, so that the guide ring6 can be fitted and welded, at 61, to the sleeve portion 60.

The sub-assembly described above does of course include the abutmentmeans in accordance with the invention.

As will be apparent from the drawings, the tangential tongues 40 and thedrive member 44 are mounted radially in a region in which the transversewall 2 extends in axial projection away from the piston 9 and away fromthe turbine wheel 4, with respect to the central portion of the saidwall.

Thus the axial length between the piston 9 and the wall 2 is reduced inthe region of the collar portion 8 of the ring 6, and use is made of theconfiguration of the wall 2 so as to locate the tongues 40 and themember 44 without increasing axial size.

The present invention is of course not limited to the embodimentdescribed. In particular, the torsion damper 23 may take some otherform, for example that which is described in the document U.S. Pat. No.5,209,330.

In another version, one of the liners 11 may cooperate indirectly withthe transverse wall 2.

In general terms, the liners 11 are gripped directly or indirectlybetween the piston and the wall 2.

In a further version, the friction liners 11, instead of being fixed tothe disc 10 by adhesive bonding or brazing, may be fixed respectively tothe piston 9 or to the wall 2, and this may be achieved for example byadhesive bonding or brazing, so that each friction liner is fixed to oneof the elements, consisting of the piston and the transverse wallrespectively, between which it is arranged to be gripped.

The structures of the coupling 13 may of course be reversed, with thedisc 10 then having mortices in which tenons of the guide ring 12 areengaged.

In a further version, the disc 10 may be coupled by means of a couplingof the tenon and mortice type to a crown which is carried on the turbinewheel 4. In that case, the disc 10 is coupled rigidly to the turbinewheel 4.

In FIGS. 3 and 4, the number of abutments 46, 247 does of course dependon the application. Thus, certain of the tongues may be not associatedwith abutment means.

The seal 29 may be carried by the piston 9, and more precisely by thesleeve portion of the latter.

It will be noted that the abutment means are favourable to theproduction of a controlled sliding movement between the disc 10 and theassembly consisting of the piston 9 and the wall 2.

Thus the friction liners 11 may be provided with grooves, for coolingthem during the said controlled sliding movement, such as is describedfor example in the document U.S. Pat. No. 5,339,230.

In a modified version, the grooves may be in the form of portions of aspiral.

The piston 9 may be coupled in rotation, with axial mobility, to thetransverse wall 2 by means of a supplementary member which is riveted tothe piston, in the manner described in the document U.S. Pat. No.5,209,330.

In another version, the coupling may be provided by complementarysplines, which act between the outer periphery of the collar portion 8and the inner periphery of the central sleeve portion of the piston 9.

In all cases, the abutment means may consist of rivet heads fixed to thepiston 9 and cooperating with abutment means analagous to the abutmentmeans 46 in FIG. 3. These abutment means are then carried by a membersimilar to the member 44 in FIG. 3, the said member having no tongues,while the said rivets have a head with an extension similar to theextension 147 in FIG. 4. The rivets 43 may be omitted, with the tongues40 then being integral with the member 44 being fixed to the piston 9 attheir free ends by the fastening means 41, 42.

I claim:
 1. A hydrokinetic coupling apparatus, comprising a generallytransversely orientated wall (2), which is adapted to be coupled inrotation to a driving shaft and which carries a guide ring (6) fastenedcentrally on said wall, a piston (9) which is sealingly mounted foraxial movement along the guide ring (6) and which defines, with saidring (6) and said transverse wall (2), a variable volume chamber (30)which is bounded on the outside by a disc (10), and friction liners (11)adapted to be gripped, respectively, between the piston (9) and the disc(10) and between the disc (10) and the transverse wall (2), eachfriction liner (11) being fixed to one of the elements consisting of thedisc (10) and, respectively, the piston (9) and the transverse wall (2)between which the liner is adapted to be gripped, wherein abutment means(50), facing towards the transverse wall (2) and carried by thetransverse wall (2), are provided for limiting the movement of thepiston (9) in a direction away from the transverse wall (2), and whereinsaid abutment means (50) are fitted within said variable volume chamber(30).
 2. Apparatus according to claim 1, wherein the piston (9) iscoupled in rotation to the transverse wall (2), with axial mobilitybeing provided by means of resilient tangential tongues (40) fixed to anannular member (44), which is itself fixed to the transverse wall (2),and in that the said abutment means (46) are press-formed in lugs (48)which are offset axially with respect to the main portion of the annularmember (44), and which are part of the annular member (44).
 3. Apparatusaccording to claim 2, wherein the tangential tongues (40) are extendedcircumferentially beyond their fastening to the piston (9), and in thatthe free end of the extensions is adapted to cooperate with the abutmentmeans (46) which face towards the transverse wall (2) and which arefixed to the annular member (44).
 4. Apparatus according to claim 3,wherein going from the main portion of the member (44), at least onecranked portion is defined generally in cross section with an axiallyorientated portion surrounding the free end of the tongues (40), theaxial portion being extended by a transversely orientated portiondefining the abutment means and adapted to cooperate with the dorsalface of the tongues (40) facing towards the piston (9).
 5. Apparatusaccording to claim 1, wherein the piston (9) is coupled in rotation tothe transverse wall (2), with axial mobility being provided by means ofresilient tangential tongues (40) fixed to a member (44), which isitself fixed to the transverse wall (2), in that the tongues (40) arefixed by means of rivets (43) to lugs (48) which are offset axially withrespect to the main portion of a member (44) that is fixed on thetransverse wall (2), and in that the heads of the rivets (43) areextended (247) and are adapted to cooperate with the dorsal face of thetongues facing towards the piston (9).
 6. Apparatus according to claim2, in which the tongues (40) are fixed by means of rivets (43) totongues (48) which are offset axially with respect to the main portionof the member (44) fixed on the transverse wall (2), and in which thetangential tongues (40) are fixed to the piston (9) by means of twofastening parts (41, 42), one of which (41) is fixed to the tangentialtongues (40) and has a head, wherein the head of the said fastening partis extended circumferentially (147) and is adapted to cooperate with theabutment means (46) in the form of lugs.